Method of continuous and semicontinuous casting of metals and a plant for same



Sept. 16, 196 z, ETsE v ET AL 3,46?,fi

METHOD OF con'rmuous AND SEMICONTINUOUS CASTING 0F METALS AND A PLANTFOR SAME Filed March 1, 1967 'IIIIIIIIIIII'IMIIJM United States Patent3,467,166 Patented Sept. 16, 1969 US. Cl. 16449 3 Claims ABSTRACT OF THEDISCLOSURE A method of, and an apparatus for, continuous orsemi-continuous casting of molten metal into ingots by inducing analternating electromagnetic field about the metal being cast so that theelectromagnetic forces hold the molten metal in place as a coolingmedium progressively cools the metal so its solidifies to form a skinfor the ingot being cast.

The present invention relates to methods of continuous andsemicontinuous casting of metals and plants for carrying the method intoeffect.

A method of continuous and semicontinuous casting of metals, is knownwherein the molten metal from a device, ensuring its uniform supply, isdirected into a mold, being in contact with cooled walls thereof, andpartially solidifies. It is cooled on emerging therefrom and completelysolidifies.

The known method employing moulds possesses a number of disadvantages.For instance, during the solidification of a moving ingot, it being incontact with the mold walls, various defects (blowholes, flashes) oftenform, while the formation of an air gap between the surface of the ingotand that of the mold will result in a decrease of the casting speed, theformation of surface flows, and a deterioration of the internalstructure of the ingot. The presence of the surface defects requires anadditional amount of machining ingots, thus considerably decreasing theyield of metal.

To decrease the friction between the mold and the moving ingot, in theknown method, a lubricant is required, which is likely to impair thesanitary conditions of the work and to deteriorate the cultural level ofthe production process.

The molds employed in plants for effecting the existing methods ofcontinuous and semicontinuous casting of metals are extremely expensivebecause of the requirements that must be met as to their quality ofmanufacture and heavy conditions of work.

An object of the present invention is to eliminate the foregoingdisadvantages.

The principal object of the present invention is to provide a method ofcontinuous and semicontinuous casting of metals, and a device foreffecting the same, which allows increasing the production rate ofcasting units, reducing the expenses of manufacturing equipment,improving the structure of the ingots, obtaining an ingot surface whichdoes not require machining, and improving the technical characteristicsof the production process.

In conformity with the present invention, this is achieved when carryinginto effect the continuous and semicontinuous methods of casting metalsby use of an alternating electromagnetic field induced around the streamof molten metal, said electromagnetic field setting up forces in thisstream that are directed inside the stream, and retain the metal fromflowing off laterally, thus molding it into an ingot. A cooling mediumis supplied on the surface of the forming ingot as it moves itscrystallization zone.

In the plant for carrying said method into effect, an annularelectromagnetical inductor is disposed under the tundish or other devicefor providing a uniform supply of the molten metal. In this plant, adevice is provided for supplying the cooling medium into a gap betweenthe inductor and the surface of the ingot thus formed.

The essential feature of the proposed method of continuous andsemicontinuous casting of metal is as follows.

An alternating electromagnetic field is induced around the stream ofmolten metal. This field induces an alternating electromotive force andeddy currents in the molten metal (melt). The interaction of eddycurrents with a magnetic field sets up electrodynamical forces(electromagnetical, mechanical, pondermomotive) directed inside the meltand compresses it. When compressed, the molten metal has imparted to ita defiinite shape in cross-sectional area and definite geometricaldimensions. The shape to be imparted to the melt depends upon theinductor shape, while its geometrical dimensions depend upon theintensity of the magnetic field on the metal surface.

For obtaining an ingot of the specified shape and dimensions, there isselected the frequency and current value of a generator setting up analternating electromagnetic field. A uniform magnetic field along theingot perimeter is also provided for inducing as well as for uniformcooling. The current frequency is selected in such a manner that theeddy currents induced in the melt flow along its surface layers, thatis, there should occur the surface effect (so-called skin-effect).Hence, for cylindrical ingots, the frequency is selected with dueaccount of a condition:

ingotq/ T where R is the radius of ingot in cm.; he is the equivalentdepth of the current The electrodynamical forces mold the molten metal(melt) and completely prevent it from flowing off laterally during theentire process of the ingot formation.

A cooling medium is supplied on the surface of the ingot at it isformed, and passes into its crystallization zone, so that the ingot,when cooling down, undergoes a complete crystallization.

The nature of the present invention will become more fully apparent froma consideration of an exemplary embodiment of the proposed method,featuring the casting of aluminum to be carried into effect on a plant,represented in the accompanying drawing illustrating a preferredembodiment thereof.

The plant of the present invention is comprised of an annularelectromagnetical inductor 1; a supply of molten metal is poured throughchannel 2 to a box 3 on its end having a hole 4 to provide a uniformdistribu tion of the melt to a cup or tundish 5 having a cone 6 in itscenter and holes 7 uniformly located around the perimeter of its walls8; a starter bar or dummy bar 9; a collector 10* with an annular nozzle11 whose position in the vertical plane is adjusted by screw-typelifting devices 12 provides coolant.

The process of casting aluminum is effected in the following manner.First, the appropriate frequency of the inductor current is selected.For obtaining an ingot 345 mm. in diameter, the frequency adopted isequal to 2500 hertz. The casting speed is equal to 120 mm./min.

The molten aluminum is supplied along the channel or trough 2 throughthe hole 4 of the box 3 on the starter bar 9, inserted from below insidethe inductor 1. Water employed as a cooling medium is supplied from thecollector 10 through the nozzle 11, to impinge on the dummy bar andcools the molten metal on the dummy bar 9, which begins to solidify.

The solidified portion of the melt is indicated in the drawing by theindex A, while the non-solidified (or molten) portion thereof is shownby the index B.

The electromagnetic field, induced by the inductor 1, sets up forces inthe melt and thus the liquid portion of the ingot B is retained fromflowing off, and solidifies in the shape desired.

As the height of the column of the molten metal increases, the columnbeing partially solidified and resting on the starter bar 9, the latterbegins to descend. At the same time, the cup 5 is placed on the uppersurface of the molten metal (portion B). The molten metal descends pastthe cone 6 of the cup 5, flows over its bottom, and is uniformlysupplied through the hole 7 into the magnetic field of inductor 1. Asthe molten metal is supplied inside the inductor, the molten metalsolidifies as it cools, thus forming the column of the solidified metalwhich descends together with the dummy bar. The ingot is maintained inthe vertical position by rollers 13 provided under the inductor so as tobe capable of being adjusted in the horizontal plane. Thecrystallization occurs due to water being supplied directly on thesurface of the ingot. The water is supplied into a gap between theinductor and the surface of the ingot from the collector 10 by theannular nozzle 11 disposed inside the inductor 1 concentricallytherewith and at a height approximately equal to the half of theinductor height.

As the molten metal is continuously supplied inside the inductor, theingot is solidifying therein. The ingot, on being solidified with acontinuous supply of the cooling medium (water), forms a continuouscolumn of the solidified metal which, during its vertical movement, iscut into parts without interrupting the casting process. This continuousmethod may be employed for casting steel and alloys. As for aluminum,the casting process will be semicontinuous, because at the present timethere are no methods available for its cutting, which would provide forthe continuous casting process.

The described method of casting has been tested on an experimentalplant.

The test ingots of aluminum thus obtained have a smooth surface free ofdefects and which requires no machining. The structure of the ingots wasfound to be fine-grained and sound. The ingots were employed forextrusion and forging. The mechanical testing of ingots and articlesmanufactured thereof has evidenced that they possess both a highplasticity and good mechanical properties.

What we claim is:

1. A method of continuous and semicontinuous casting of metals into aningot, comprising the excitation of an alternating electromagnetic fieldaround molten metal flowing onto the top of an ingot being cast, saidelectromagnetic field setting up forces inside the molten metalrestraining the metal from flowing laterally off the ingot and supplyinga cooling medium on to the surface of the metal to solidify it into aningot and withdrawing the ingot downwardly as it solidifies.

2. A plant for continuous and semi-continuous casting .of metals intoingots, comprising a device for a uniform supply of molten metal to thetop of an ingot being poured; an annular inductor disposed below butadjacent said device for a uniform supply of the molten metal forproviding a force to hold the molten metal on top of the ingot; a gapbetween said inductor and the surface of the ingot being cast; a meansfor supplying a cooling medium into said gap, and means for moving themetal progressively downwardly as it is cooled and solidifies.

3. A plant according to claim 2, wherein a means for supplying thecooling medium is essentially an annular nozzle disposed concentricallywith said inductor.

References Cited UNITED STATES PATENTS 2,686,864 8/1954 Wroughton et al.164-49 X 2,963,758 12/ 1960 Pestel et al. 164-82 X FOREIGN PATENTS1,130,892 10/1956 France.

693,267 6/1953 Great Britain. 173,173 11/1960 Sweden.

J. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, Assistant ExaminerUS. Cl. X.R. 164-48, 82, 250

